In a water circulation system, several different devices are connected together to properly treat the water. For example, one of the following four configurations of the various components is generally used in conjunction with a swimming pool water circulation system:
(1) a pump, a filter, a heater, and a chlorinator, connected in series, in that order; PA1 (2) a pump, a filter, and a chlorinator, connected in series, in that order; PA1 (3) a pump and a filter connected in series, with a heater and a chlorinator connected to the filter in parallel; and PA1 (4) a pump, with a filter and a chlorinator connected to the pump in parallel (however, this combination is the least desirable, as all the water is not filtered).
In any of the above configurations, it is usually necessary to insert a check valve into the system upstream of the chlorinator to prevent concentrated chlorine solution from bleeding back upstream from the chemical feeder into the circulation system. A check valve is usually necessary because the chemical feeders of the prior art are constructed such that the inlet and outlet ports are typically located near the bottom of the chemical feeder. This location for the inlet and outlet ports creates a problem because as water flows through the chemical feeder, the water is mixed with the chemical tablets in the lower portion of the feeder, creating a concentrated solution that is located near both the inlet port and the outlet port.
In a swimming pool water circulation system using chlorine tablets in the chemical feeder, the concentrated solution is chlorinated water, which is heavier than regular water and tends to sink toward the bottom of the chemical feeder. In addition, the less-chlorinated water column located above the more-chlorinated water creates a pressure head on the more-chlorinated water. This pressure head is in proportion to the size of the water column; i.e., large chemical feeders allow for large water pressure heads which create a higher pressure on the more-chlorinated water. The net effect is that gravity and the pressure created by the pressure head act to force the more-chlorinated water from the bottom of the feeder and into the outlet flow of the feeder. But because both the inlet and the outlet are located at the bottom of the feeder, the more-chlorinated water has a tendency to bleed back through the inlet and into the upstream water flow. This problem is especially prevalent when the system is not running.
Having the more-chlorinated water flow back upstream is detrimental to the overall water circulation system, in that it can damage the upstream system parts, including corroding the copper contained within a heater. While the upstream bleeding may be of small volume, it is still a concentrated solution, and the damage caused thereby can be significant.
One example of this type of device is Hayward Pool Products, Inc.'s model CL-200 In-Line Chlorinator. This chlorinator has an inlet and an outlet located at the bottom of the body of the device. The top cap of the device is removed and chlorine tablets are placed into the hollow interior of the body. When in operation, highly chlorinated water will be at the bottom of the device, which could lead to the upstream bleeding problem described above.
A device that has water flowing through its top, as opposed to its bottom, is disclosed in U.S. Pat. No. 5,507,945. The device disclosed in the '945 patent employs a cap attached on top of a canister, with a flow conduit extending through the cap. A solid chemical is placed into a container, which is positioned inside the canister. As water flows through the conduit, a small portion is directed into the canister. As the canister fills with water, some of the water enters the container, dissolving the solid chemical. The resulting chemical solution is taken from the top of the container by venturi forces within the conduit.
There is presently a need in the art for a chemical feeder that reduces the backflow problem described above. The present invention satisfies that need and, in many applications, may eliminate the need to install a separate check valve upstream of the chemical feeder.